1. Field of the Invention
The present invention relates to an image reading apparatus for reading an image recorded on a film original such as a developed photographic film.
2. Description of Related Art
The structure of a conventional film scanner serving as an image reading apparatus will be described with reference to FIGS. 20 through 24.
FIG. 20 is a perspective view showing the structure of the conventional film scanner. FIG. 21 is a block diagram showing the schematic structure of the film scanner shown in FIG. 20. Furthermore, FIG. 22 is a block diagram showing the circuit structure of the film scanner shown in FIG. 20.
Referring to FIGS. 20 and 21, a developed film 102 is fixed on a film carriage 101 which is used as an original placing board. Light emitted from a lamp 103 which is a light source passes through the film 102 and is then reflected by a mirror 104 to be imaged by a lens 105 on a line sensor 106 which is composed of a CCD.
A motor 107 moves the film carriage 101 in scanning directions (directions of arrows in FIGS. 20 and 21), and a sensor 108 detects the position of the film carriage 101. Reference numeral 109 denotes an optical axis directed from the lamp 103 to the line sensor 106, reference numeral 110 denotes a control circuit, and reference numeral 111 denotes a lens holder arranged to hold the lens 105. Reference numeral 112 denotes an exterior case of the film scanner, and reference numeral 113 denotes an input and output terminal.
The lamp 103, line sensor 106, motor 107, sensor 108, and the input and output terminal 113 are electrically connected to the control circuit 110. Further, the control circuit 110, as shown in FIG. 22, is composed of a film scanner control circuit 110-1, a sensor control circuit 110-2, a motor control circuit 110-3, an image information processing circuit 110-4, a lamp control circuit 110-5, a line sensor control circuit 110-6, a quantity-of-light detecting circuit 110-7, and a motor-driving-speed deciding circuit 110-8.
Next, the method of reading image information recorded on the film 102 will be described.
First, when a film reading command is inputted from the external through the input and output terminal 113, the position of the film carriage 101 is detected by the sensor 108 and sensor control circuit 110-2. This position information is transmitted to the film scanner control circuit 110-1. Then, in order to make the film carriage 101 stand ready at a predetermined standby position, the motor 107 is driven by the motor control circuit 110-3, and hence the film carriage 101 is moved to the standby position. Furthermore, the lamp control circuit 110-5 turns on the lamp 103, and rough scanning is performed by rotating the motor 107 at a predetermined speed by the motor control circuit 110-3 so as to scan an image area of the film 102 at a predetermined speed in the direction of a film plane. During this rough scanning, image information is transmitted to the line sensor control circuit 110-6 by the line sensor 106.
Next, the film carriage 101 is moved to the predetermined standby position by rotating the motor 107. Then, fine scanning is performed by rotating the motor 107. During this fine scanning, image information is transmitted from the line sensor 106 to the image information processing circuit 110-4 through the line sensor control circuit 110-6. When the fine scanning is completed, the lamp control circuit 110-5 turns off the lamp 103, and at the same time, the image information processing circuit 110-4 performs image information processing. Moreover, the image information is outputted from the input and output terminal 113, and the operation of the film scanner is terminated.
Since the above conventional film scanner is adapted to read only a specific kind of transparent original (developed photographic film), it is not possible to read a different kind of transparent original such as a transparent original contained in a dedicated cartridge.
In addition, since a loading slot for inserting a strip film holder or a slide-mounted film is always opened in the above conventional film scanner, there is a possibility of dust entering from the loading slot. The dust entering inside the film scanner adheres to a surface of the lamp, which is an internal light source, and to optical parts such as a mirror, and hence leads to nonuniformity of the light source and reduction of luminous intensity. As a result, there happens a problem of decreasing the quality of a read image.